Nozzle material firing evaluation means and system



2 5 3 imm? 6 O Ming-AQ.; E www Jan. 19, 1965 H. woLFF 3,165,924

MozzLE MATERIAL EIRING EVALUATION MEANs AND sYsTEM Filed July 18, 196sPRSSl/! /f I 20 l I l: I I 23 l INVENTOR.

" WO FF United States Patent C) 3,165,924 NOZZLE MATERIAL FIRINGEVALUATION MEANS AND SYSTEM Harry Wolff, Los Gatos, Calif., assigner tothe United States of America as represented by the Secretary of the AirForce Filed July 18, 1963, Ser. No. 296,146 4 Claims. (Cl. 73-116) Thisinvention relates to testing and evaluating means, and moreparticularly, to a system and means for evaluating nozzle material forrocket type motors and similar devices.

The evaluation of nozzle material for jet and rocket propulsion devicesis a relative procedure wherein the performance of a sample material is`compared to a known standard. In practice, materials are frequentlyevaluated as a nozzle insert in a solid propellant test motor fired `atspecific chamber pressures and durations. Efforts have been made tominimize tiring to firing Vaniations and maintain identical testconditions necessary for satisfactory evaluation, but these goals arenot frequently met. The major difficulty lies in repeating the testchamber pressure time history exactly since ablation characteristics ofdiierent types of materials are not uniform and the resulting change innozzle throat area also affects the solid propellant motor chamberpressure. Variation in chamber pressure is, in effect, a continuouschange in test conditions that complicates and, in fact, preventseffective exact comparison of a sample material with a known standardmaterial, for instance, the material used in the nozzles or nozzleinserts of jet and rocket motors, and the like.

Efforts have also been made with gaseous oxygengaseous hydrogenpropellant test motors both With and without the addition of substancesintended to simulate the combustion products of solid propellants. Thesedevices provide the time necessary for sucient ablation of a nozzleinsert to reduce chamber pressure to a predetermined level at which timethe test is terminated. However, simulated combustion products obtainedby these propellants do not match solid propellant exhaust products andpose technical difficulties in metering various solid additives to thebasic gaseous propellants.

The present invention eliminates the above-mentioned ditculties andobjections by providing a simple selfcontained unit which providespressure time conditions over the full duration of the test. Solidpropellant is employed to provide correct exhaust products with noproblems of valving and metering of gaseous propellants or additives.

An object of the invention is to provide a direct means for comparing asample material, such as used in a nozzle or nozzle insert in a jetmotor against a known standard material for the same purpose underidentical test conditions for the full test duration.

A further object of this invention is the provision of a testing devicefor material which goes into the manufacture of rockets and jet motorsand is subject to some ablation due to heat and pressure, in which asample of the material is simultaneously subjected to the same identicalconditions of heat and pressure during a full time duration of test witha standard known material to establish an accurate comparison of theperformance of the sample material with the standard material, in whicha wide variety of heat and pressure conditions may be provided.

A further object is the provision of simple means for comparing a sampleexhaust nozzle insert simultaneously with a similar standard nozzleinsert under identical pressure and identical time durations in whichpressure and ICC heat are supplied simultaneously from a solid fuelpropellant.

More particularly, a further object is the provision of a solid fuelpropellant combustion chamber having means at one end for receiving astandard exhaust nozzle made of a known standard material and means atthe opposite end of the combustion chamber for receiving a similarexhaust nozzle made of a test material to be evaluated, tested andcompared with the aforesaid known sample, including means for insertingand tiring a solid propellant in said combustion chamber, whereby bothexhaust nozzles are subjected to identical propellant pressure, heat andduration conditions to provide an accurate comparison between thenozzles and the material therein under identical conditions of test.

A further object is the provision of a device having an elongatedcylindrical combustion chamber having identical removable nozzleassembly ends for receiving a solid propellant therebetween, and meansin each of said receivable ends for removably receiving an identicalrocket type exhaust nozzle insert therein, whereby a nozzle insert ofstandard known material can be inserted in one of said assembly ends andan identical sample nozzle insert made of a material to be compared withthe standard material of the other nozzle can be inserted in theopposite end nozzle assembly and compared for ablation, when a solidfuel propellant is inserted in said combustion chamber between thenozzles and ignited.

A further object includes a construction just mentioned, including meansfor indicating combustion chamber pressure throughout the duration ofcombustion of the propellant in the combustion chamber.

Other objects and advantages of the invention will become apparent fromthe following description and accompanying drawing which illustrates aside view of the testing device of the invention with the upper halfbroken away and shown in section, and also with the combustion chamberbroken away intermediate its ends and foreshortened.

Referring to the drawing, the reference numeral 1 denotes a cylindricalcombustion chamber supported horizontally intermediate its ends by asupport bracket 2. The opposite ends of the combustion chamber areidentical and terminate iri enlarged head members 3 and 4, each formedwith internal cylindrical bores 3a and 4a for receiving .the nozzleinsert holding assemblies 5 and 6.

These assemblies 5 and 6 are identical and, therefore, the samereference numerals will be used in connection with the parts thereof,except that one of the assemblies, for instance the assembly 6, will bedenoted mostly by primed reference numerals while the assembly 5 willnot employ primed reference numerals.

The assemblies 5 and 6 comprise tubular flanged insents 7*7 fitting therecesses 3a and 4a respectively and being removably retained thereinagainst the faces 3b and 4b by the annular split snap rings 8 and 8seated in the grooves or internal annular channels 9 and 9.

In the periphery of each ange portion is an annular recess 10-10 havinga conventional `O-ring therein, preventing leakage between the interiorof the heads 3 and 4 and the flanged tubular members 7 and 7.

The tubular members 7 and 7 are each threaded externally, as indicatedat 11 and 11', and formed with end shoulders 12-12. The internalcylindrical bores 13-13 are dimensioned to receive identical test items,such as the respective socket nozzles or nozzle inserts 14 and 15. Thesenozzle inserts are identical in size and shape, each having an annularhead portion 14a and 15a and a smaller diameter extension 14b and 15bwhich fits the bores 13 or 13 in the members '7 and 7.

The nozzle inserts 14 and 15 each have an annular channel 14a` and 15cin which is disposed an O-ring to prevent leakage between the exteriorof the nozzle inserts 14 and 15 and the bores 13 and 13.

The throats 16 and 16 of the nozzle inserts 14 and 15 are shown alsoidentical and the inserts are retained in the nozzle assemblies by theinternally threaded nozzle retainer members 17 and 18, threaded on thethreaded portions 11 and 11 ofthe members 7 and 7.

The outer faces 17a and 18a of the nozzle retainer members 17 and 18,carry nozzle insert retainer rings or apertured plates 19 and 19 whichoverhang the ends of the nozzle inserts for retaining the nozzle inserts14 and 15 against the shoulders 12 and 12', preventing axialdisplacement of the nozzle inserts during operation of the device.

Removing one or both of the nozzle assemblies or 6 permits thecylindrical chamber 1 to be loaded, for instance by solid propellant jetfuel, such as indicated at 20, which may be two one pound cartridgeloaded propellant grains, with a separating spacer 20 therebetween toprovide room for a central chamber pressure transducer tap 21 for apressure transducer and pressure gauge 22, or recorder of conventionalconstruction to measure or record the chamber pressure during the testoperation of the device.

Chamber pressure achieved is a function of predetermined ballisticparameters and is identical throughout the combustion chamber 1 and inthe throat sections of both nozzle inserts 14 and 15.

Ignition is simply achieved by any suitable means, such as a pyrotechnicbag igniter 23 placed on the grain 20 in the center of the motor and, inpractice, the igniter is actuated electrically and the propellant grainis ignited.

As one or both of the throats 16-16 ablate, chamber pressure is reducedbut it is always identical in both nozzle inserts throughout theeffective burning time.

When a nozzle insert made of a standard known material and constructionis inserted in one nozzle, assembly members 5 or 6 and a nozzle insertwhich is made of a different material or construction is inserted in theother nozzle assembly member for the purpose of comparing the behaviorof the sample and the standard material nozzle, it is evident thatduring the duration of the test both materials will be subjected toidentical test conditions.

The invention therefore provides a direct means for comparing a samplematerial against a standard material under identical heat and pressuretest conditions for the full test duration, and the device may beemployed with a wide variety of solid propellants to duplicate useconditions.

Also the device may be scaled to any size desired. Furthermore, theprinciple and method may be extended to provide evaluation of nozzlematerial for liquid, gaseous, hybrid, and slurry propellant systems.

Removal of the plates 19 and 19 by removal of the screws permits thenozzle inserts 14 and 15 to be removed from the nozzle assemblies 5 and6, while removal of the snap rings 8 and 8 permits the flanged tubularmember 7 and 7 to be removed from the combustion chamber heads 3 and 4,and also provides for loading the combustion chamber 1 with suitablepredetermined propellants for a test.

The nozzle material evaluation test motor is, of course, rigidly mountedor bolted through the support bracket 2 to a `suitable rigid supportbefore making a test.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexmaple only, and is not to be taken by way of limitation, the spiritand scope of the invention being limited only by the terms of theappended claims.

I claim:

1. A rocket nozzle material evaluation test motor comprising anelongated cylindrical combustion chamber open at its opposite ends, arocket nozzle receiving assembly removably carried by each end of thecombustion chamber Shaped to receive a similarly shaped nozzle inserttherein with said nozzle inserts facing in opposite directionsconcentric to the axis of the combustion chamber, means carried by eachof said rocket assemblies for removably securing one of said rocketnozzle inserts therein against outward movement away from saidcombustion chamber, whereby when a propellant means is introduced insaid combustion chamber and fired both of said nozzle inserts will besimultaneously subjected to identical heat, pressure and test durationconditions so as to compare the durability of one of sai-d nozzleinserts in one of said nozzle assembles with the other nozzle insert inthe other nozzle assembly simultaneously under identical combustionpressure, heat and test duration conditions.

2. A device for the evaluation and comparison of a sample jet nozzlewith a standard jet nozzle of similar conguration to simultaneouslycompare the relative ablation in the throat portion of the sample jetnozzle with the standard jet nozzle comprising, an elongated cylindricalcombustion chamber having an enlarged cylindrical head portion at eachend thereof, said head portions each having a similar cylindrical boretherein extending inwardly toward said combustion chamber concentric tothe axis of said combustion chamber, a pair of similar jet nozzleholding assemblies each having an annular flange portion slidablyfitting said bores, means between said head portions and assemblies forremovably securing said assemblies in said bores, said jet nozzleassemblies each having a imilarcylindrical extension adapted to extendoutwardly away from said combustion chamber and dimensioned internallyto receive one of said similar standard and sample jet nozzles therein,cylindrical concentric nozzle retaining means removably connected toeach of said cylindrical extensions for retaining one of said jetnozzles in one of said assemblies at each end of said combustion chamberconcentric to the axis thereof, said combustion chamber adapted toreceive a solid fuel jet propellant therein between the ends thereof,and means for igniting said propellant, whereby the throat portions ofboth of said nozzles will be simultaneously subjected to identical heat,pressure and time duration conditions during the combustion of saidsolid propellant, to simultaneously compare the ablation of the materialin the throat portions thereof.

3. A testing device for simultaneously testing and comparing theablation of the material in a test jet' nozzle with the material in aknown standard similar jet nozzle under identical test conditions as setforth in claim 2, including pressure indicating means responsive topressure within the combustion chamber throughout the duration of thecombustion of a propellant when fired within said combustion chamber.

4. A testing and comparison device for comparing the ablation ofmaterial in a test sample jet nozzle with the ablation of material in astandard known similar jet nozzle simultaneously under identical heat,pressure and time duration conditions comprising, a cylindricalcombustion chamber, separating spacer ring means therein substantiallymidway between the opposite ends of the combustion chamber, saidcombustion chamber adapted to receive cartridge loaded solid propellantmeans therein between said spacer means and each end of the combustionchamber, means for simultaneously igniting said propellant means,pressure indicating means connected to said combustion chamber adjacentsaid separating spacer for indicating pressure within said combustionchamber during the combustion of saidsolid propellant means, nozzleassembly means removably secured to the opposite ends of the combustionchamber `for removably xing a similar contoured jet nozzle, concentricto the axis of said combustion chamber, in sealed relation to saidcombustion chamber, with said nozzles extending outwardly away from theopposite ends of the combustion 6 chamber in axial alignment with eachother, whereby pressure and time duration and the relative ablationtherewhen a test sample jet nozzle is xed in one of said between Can bedetermined. nozzle assembly means and a standard known jet nozzle isfixed in the other nozzle assembly means at the oppo- References Citedby the Examiner site end of the combustion chamber and the propellant 5UNITED STATES PATENTS cartridge loaded propellant means is ignited theablation 3,112,641 12/63 Gerhardt 73 86 0f the material in the throatportions of the test sample 3,112,669 12/63 Damblanc 60 35 6 nozzle andthe ablation of the material in the standard known nozzle at theopposite end of the combustion RICHARD C' QUEISSER Primary Exammer'chamber are subjected to identical conditions of heat, 10 DAVIDSCHONBERG, Examiner-

1. A ROCKET NOZZLE MATERIAL EVALUATION TEST MOTOR COMPRISING AN ELONGATED CYLINDRICAL COMBUSTION CHAMBER OPEN AT ITS OPPOSITE ENDS, A ROCKER NOZZLE RECEIVING ASSEMBLY REMOVABLY CARRIED BY EACH END OF THE COMBUSTION CHAMBER SHAPED TO RECEIVE A SIMILARLY SHAPED NOZZLE INSERT THEREIN WITH SAID NOZZLE INSERTS FACING IN OPPOSITE DIRECTIONS CONCENTRIC TO THE AXIS OF THE COMBUSTION CHAMBER, MEANS CARRIED BY EACH OF SAID ROCKET ASSEMBLIES FOR REMOVABLY SECURING ONE OF SAID ROCKET NOZZLE INSERTS THEREIN AGAINST OUTWARD MOVEMENT AWAY FROM SAID COMBUSTION CHAMBER, WHEREBY WHEN A PROPELLANT MEANS IS INTRODUCED IN SAID COMBUSTION CHAMBER AND FIRED BOTH OF SAID NOZZLE INSERTS WILL BE SIMULTANEOUSLY SUBJECTED TO IDENTICAL HEAT, PRESSURE AND TEST DURATION CONDITIONS SO AS TO COMPARE THE DURABILITY OF ONE OF SAID NOZZLE INSERTS IN ONE OF SAID NOZZLE ASSEMBLIES WITH THE OTHER NOZZLE INSERT IN THE OTHER NOZZLE ASSEMBLY SIMULTANEOUSLY UNDER IDENTICAL COMBUSTION PRESSURE, HEAT AND TEST DURATION CONDITIONS. 